To obtain the wave crest pattern generated by a point obstacle, we use the kinematic
approach [1]}. We consider the two-dimensional problem in the rest frame with the
obstacle at the origin and the flow velocity vector \(\mathbf {V}=(-V,0)\) .
In this frame of reference the stationary wave crests do not move. The condition of that is
\(\hbar \omega (k) = E_0(k)-\hbar k V \cos \xi =0,\) 
